The present invention is directed to improvements in dampers. More particularly, the present invention is directed to surface effect dampers that produce a damping force which includes both hysteretic and frictional components.
This development is related to the invention described and claimed in U.S. patent application Ser. No. 07/811,758, entitled "Dual-Rate Surface Effect Dampers" filed Dec. 20, 1991 and now U.S. Pat. No. 5,183,137. That application is hereby incorporated by reference.
The principle of operating a hysteresis damper is that translational or rotational energy is dissipated by working an elastomeric element (e.g., a rubber element) to convert that kinetic energy into heat energy. In the past, in order to function properly as a hysteresis damper, the amount of energy dissipated through hysteresis had to be significantly greater than the energy dissipated through friction, or the durability of the elastomeric element would be inadequate to warrant usage. By minimizing friction damping, the damping capabilities of the device were significantly limited.
The key patent in the development of hysteresis dampers is U.S. Pat. No. 3,232,597, issued to Haydecki. Many different conceptual aspects of hysteresis dampers are dealt with in the Gaydecki patent, which discloses a large number of embodiments in its specification and includes twenty-six figures. Still, in the over twenty-five years since Gaydecki initiated development of the concept of hysteresis dampers, very little has been done with them. This dirth of activity is in spite of the tremendous potential of such devices have to overcome the problems associated with hydraulic dampers and gas springs. Hydraulic dampers and gas springs have elements that are required to function as both seals and bearings. As the bearing element wears, it will necessarily lose the close tolerance it originally had with the slidable member, resulting in its inability to seal properly and, eventually, loss of hydraulic or pneumatic pressure. Once wear has progressed to that point, the useful life of such a damper is ended and costly replacement is necessary.
It is the purpose of this invention to devise various improvements in dampers which utilize hysteresis damping to enable them to realize their full potential. The surface effect damper of the present invention combines friction damping with hysteresis damping to increase the available damping force without adversely effecting wear life of the damper. Further, the features of the present invention make the surface effect damper better suited for a variety of applications.
One such improvement includes a feature by which the damper is made amplitude sensitive, that is, it has a decoupler mechanism to eliminate or greatly reduce the damping for low amplitude input conditions (normal operating conditions), as compared to the damping available for high amplitude inputs, (resonances or shock loading). This type surface effect damper could be used in place of a conventional shock absorber.
Another feature of the present invention is the provision of means to increase the damping force in a non-linear manner in response to increased amplitude due to shock loading. This feature provides a steadily increasing braking force for dissipation of energy. Such a non-linear feature is useful in applications such as shock absorbers and the like.
Another embodiment is designed to provide significantly greater damping in one direction than in the other. Such a surface effect damper could readily be used in place of a conventional gas spring.
Still another embodiment provides an improved rotational surface effect damper useful for damping rotational motion. Such a device could be adapted for use as a rotational brake or used as a rotational resonance damper for any number of different applications (vehicles, machinery, etc.).
Yet another embodiment of the present invention sets forth a multiaxial damper which can be used, for example, as a motor mount. This embodiment has the capability for the piston to tilt or misalign relative to the axis of its piston rod. In this manner, certain torsional vibrations of the engine can be both accommodated and damped. This embodiment constitutes an improved configuration, for some applications, over the mount set forth in Applicant's earlier U.S. Pat. No. 4,957,279, which is herein incorporated by reference.
Various other characteristics, features and advantages of the dampers of the present invention will become apparent after viewing the attached drawings and reading the following detailed description.